Change the return value of dup() for Vmo<Rights>

kernel/aster-nix/src/fs/utils/page_cache.rs

@@ -45,7 +45,7 @@ impl PageCache {
     // TODO: The capability is too high，restrict it to eliminate the possibility of misuse.
     //       For example, the `resize` api should be forbidded.
     pub fn pages(&self) -> Vmo<Full> {
-        self.pages.dup().unwrap()
+        self.pages.dup()
     }
 
     /// Evict the data within a specified range from the page cache and persist